In special editions, thermal forming packaging machines of the Applicant are known which produce packagings with an undercut. The undercut is formed into the lower foil by means of a lifting unit for the forming station which is arranged at an inclination with respect to the transport plane of the lower foil and the transport direction, preferably assisted by a die. The undercut is produced on a side of the deep drawn packaging tray which is parallel to the transport direction. The undercut may reach until below the sealed seam of the packaging, in order to obtain a possibility for upright standing of the packaging. However, with a lifting unit arranged at an inclination and a correspondingly inclined movement of the lower tooling of the mould, it is disadvantageous that the side of the packaging tray which is opposite the side with the undercut is formed parallel to the undercut, but inclined towards the interior of the packaging tray. This is necessary in order to avoid a collision of the molded packaging tray with the lower deep drawing die when opening the forming station. Hence, in a side view, the packaging is shaped in a rhomboid form.